Rheology of surfactant solution Nonlinear extension of tread like micelles and shear induced structure

研究了十六烷基三甲基溴化铵（CTAB）和玻璃酸钠（NaSal）水溶液的非线性流变学，以研究线状胶束的有限伸展性和剪切诱导结构。CTAB的浓度固定在0.1 mol/L<-1>，NaSal的浓度在0.07至0.4 mol/L之间变化<-1>。对于所有测试溶液，用具有单个弛豫时间τ的麦克斯韦模型描述动态模量。测量了稳态剪切流开始后剪切应力σ和第一法向应力差N_1随时间的变化。对于低浓度的NaSal溶液，当剪切速率γ超过τ^时，在一定应变下观察到应变硬化，σ和N_1发散<-1>。对于具有高NaSal浓度的溶液，在τ^与某一临界速率γc之间的τ ^处观察到类似于普通缠结聚合物溶液的应力过冲<-1>，而在γ &gt; γc处观察到应变硬化。对于弹性固体，一个简单的关系式N_1/σ= γ，其中γ是剪切流施加的应变，对应变硬化区的所有解都成立。应变硬化是由应变相关的剪切模量引起的，可以用网络理论来描述。在非线性流变测量中，我们发现流变数据与锥板夹具的材料有很大的关系。应变硬化行为测量玻璃锥板夹具显着减弱。因此，我们研究了玻璃锥板夹具的表面处理的效果。我们发现，疏水处理是相当有效的观察硬化行为的线状胶束溶液。剪切诱导的结构后观察到的切流被发现取决于表面处理。

Nonlinear rheology of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium calicylate (NaSal) were investigated in order to study the finite extensionability of thread-like micelles and the shear induced structure. The concentration of CTAB was fixed at 0.1 mol l^<-1>, and the concentration of NaSal was varied from 0.07 to 0.4 mol l^<-1>. For all test solutions, dynamic moduli were described with the Maxwell model having a single relaxation time, τ. Time evolutions of the shear stress, σ, and the first normal stress difference, N_1, after inception of the steady shear flow were measured. For solutions having low NaSal concentrations, strain-hardening was observed and σ and N_1 diverged at a certain strain when the shear rate, γ, exceeded τ^<-1>. For solutions with high NaSal concentrations, stress overshoot similar to that of ordinary entangled polymer solutions was observed at ^between τ^<-1> and a certain critical rate, γc, while the strain-hardening was observed at γ > γc. A simple relationship for elastic solids, N_1/σ= γ with γbeing the strain imposed by shear flow, held for all the solutions in the strain-hardening regime. The strain-hardening was attributable to the strain dependent shear modulus and well described with the network theory considering finite extensibility of network strands.In nonlinear rheological measurements, we found that the rheological data significantly depend on the material of cone-plate fixture. Strain hardening behavior measured with glassy cone-plate fixtures was remarkably weakened. Therefore, we examined the effect of surface treatments of glassy cone-plate fixtures. We found that hydrophobic treatments is quite effective to observe hardening behavior of the thread-like micelle solutions. Shear induced structure observed after cession of shear flow was found to depend on the surface treatments.